Prevalence of the commensal barnacle Xenobalanus globicipitis on cetacean species in the eastern tropical Pacific Ocean, and a review of global occurrence.
Barnacles of the superfamily Coronuloidea live as obligate commensals on sea turtles, cetaceans, sirenians, sea snakes, and crustaceans (Newman and Ross, 1976). The monotypic Xenobalanus globicipitis Steenstrup, 1851 (herein referred to by genus) is specialized for living as a commensal on whales and dolphins (Darwin, 1854). The typical six-plate balanomorph shell is small and is imbedded into the skin of the cetacean host. The membrane supporting the operculum is greatly elongated, so that externally Xenobalanus resembles a pedunculate barnacle. This species is most commonly observed on the trailing edges of the dorsal fin, pectoral flippers, and tail fluke of the host, although it has been reported in areas such as the rostrum and the area between the teeth (Samaras, 1989). Xenobalanus does not receive nutrition from its cetacean host and therefore is not considered a parasite. Instead, as a suspension-feeding cirriped, it uses the water flow around swimming cetaceans and benefits from being transported by its host (phoresis). This species is highly specialized to live on cetaceans (Seilacher, 2005) and it has been suggested that its hermaphroditic reproduction may be synchronized with that of its host (Dollfus, 1968; Fertl, 2002). A five-to six-month reoccurrence cycle has been reported for Xenobalanus (Van Waerebeek et al., 1993; Orams and Schuetze, 1998), which may indicate that its life span may be of similar length or that occurrence is correlated with seasonal environmental conditions. Xenobalanus has been reported on 30 cetacean species worldwide and has a prevalence ranging from 0.5% to 55% of individuals in each sighting. However, intensity is highly variable, and there are some reports of greater than 100 barnacles on a single host (Aznar et al., 2005).
We examined the presence of Xenobalanus on cetaceans in the eastern tropical Pacific Ocean (ETP). Based on photographs taken during research cruises from 1977 through 2003, mean prevalence, mean intensity, and geographic distribution are described for Xenobalanus on 22 host cetacean species. In addition, peer-reviewed literature on this subject is examined, updating a previous summary of the cetacean hosts of this barnacle (Rajaguru and Shantha, 1992).
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Materials and methods
Cetaceans were photographed during a 2-ship, 4-month research cruise in 2003, covering 26,000 km of transects surveyed for marine mammals (boundaries shown in Figs. 1 and 2). Camera equipment included Canon EOS 10D and D60 digital cameras (Canon USA, Lake Success, NY) with 75-300 mm image-stabilized zoom and 400-mm fixed lenses. Date, latitude and longitude, cetacean species (as identified by trained cruise personnel), and unique sighting number per cetacean group were recorded with each photograph. In the laboratory, additional data were recorded upon examination of photographs, including the number of usable photographs in the sighting (as described below), number of individual cetaceans identified in the sighting, number of individuals infested with Xenobalanus, and number of Xenobalanus present. If barnacles were clumped in such a way as to compromise the accuracy of the count, the maximum number of discernible barnacles was recorded. The resolution of the digital photographs was such that in most cases, individual barnacles were easily identified.
In external appearance, Xenobalanus may be confused with the parasitic copepod Pennella balaenoptera (Evans, 1994) or the stalked barnacle Conchoderma virgaturn (Ruppert et al., 2004). However, the much larger P. balaenoptera usually occurs along the flanks, whereas Xenobalanus is generally found along the trailing edges of the dorsal fin, pectoral flippers, and the fluke, as has been described for stranded and live cetaceans. Similar to P. balaenoptera, C. virgatum requires a less specific position for attachment, requiring any hard substrate (such as another barnacle, a tooth, or exposed bone), and C. virgatum is considerably lighter in coloration than Xenobalanus. Digital photographic quality was sufficient for accurate identification of the commensal Xenobalanus; no specimens were obtained for direct examination.
During the cruise, typically many photographs were taken for each sighting. For our study, usable photographs had 1) to be in focus, 2) to be of sufficient resolution to identify a barnacle if present, and 3) to include at least one cetacean dorsal fin. For large schools, only one photograph per school was used in order to prevent recounting individuals. For small schools, only photographs of animals identifiable as individuals, either from field notes or from unique markings or pigmentation, were used. Photographs used represent a subsample of individuals and did not include every animal observed. Killer whales (Orcinus orca) were studied in additional detail, by using photographs taken on previous cruises dating back to 1977, and including photographs from the ETP in the California and Mexico killer whale catalog (Black et al., 1997).
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Two measures of prevalence of Xenobalanus were calculated for each cetacean species with at least three sightings with usable photographs. Prevalence was calculated for each sighting by dividing the number of individual whales or dolphins with barnacles by the total number of individual cetaceans identified. Mean prevalence and its standard error for each species were calculated from these values. Prevalence per sighting was calculated for each species by dividing the number of sightings with barnacles present by the total number of sightings. Mean barnacle intensity was calculated as the total number of barnacles observed on a host species divided by the number of infested hosts of the same species (Bush et al., 1997). To relate barnacle presence to primary productivity, the presence or absence of Xenobalanus at each cetacean sighting in 2003 was plotted on a map of average surface chlorophyll concentration in the ETP that was based on data provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and GeoEye.
Several statistical tests were performed to determine significant differences among the data. A nonparametric Mann Whitney-U test was used to determine if the rates of prevalence differed between Mysticetes and Odontocetes and a nonparametric Kruskal-Wallace test was used to determine if the prevalence rates differed significantly among species. Chi-square goodness-of-fit test was used to determine if the number of barnacles per killer whale followed a Poisson distribution. After normalization, linear regression was used to determine if the number of barnacles observed was predicted by the total number of animals observed in the sighting.
Within the ETP over 10,000 photographs of 22 cetacean species and 2510 individuals revealed that 132 individuals of 14 species were host to Xenobalanus (Table 1). Out of 497 photographed sightings, 445 were determined to be usable in the analysis, and of these sightings, 47 displayed Xenobalanus: 38 odontocete sightings and 9 mysticete sightings. Xenobalanus was not observed on seven cetacean species and on one genus for which the species could not be identified: pygmy killer whale (Feresa attenuata); Fraser's dolphin (Lagenodelphis hosei); Pacific white-sided dolphin (Lagenorhynchus obliquidens); melon-headed whale (Peponocephala electra); sperm whale (Physeter macrocephalus); false killer whale (Pseudorca crassidens), rough-toothed dolphin (Steno bredanensis); and three unidentified beaked whale individuals (Mesoplodon spp.) Of these, the barnacle has been previously reported throughout its worldwide range on pygmy killer whale, false killer whale, two species of beaked whales (Mesoplodon spp., Rajaguru and Shantha, 1992), Pacific white-sided dolphin (Dailey and Walker, 1978), and rough-toothed dolphin (Addink and Smeenk, 2001).
Four cetacean species seen in the ETP had not previously been reported as hosts of Xenobalanus: Bryde's whale (Balaenoptera edeni), long-beaked common dolphin (Delphinus capensis), humpback whale (Megaptera novaeangliae), and three forms of spinner dolphin (Stenella longirostris): eastern (S. longirostris orientalis) and the forms known commonly as whitebelly and southwestern spinner dolphins (Table 2). For Bryde's whales and humpback whales, the dorsal fin was the only visible appendage, as opposed to the long-beaked common dolphins and spinner dolphins for which pectoral flippers and tail flukes were also visible. The humpback whale individual that displayed a single specimen of Xenobalanus appeared to have a damaged dorsal fin.
Prevalence and intensity of the barnacle
Blue whales (Balaenoptera musculus) had the highest mean prevalence of the barnacle, followed by fin whales (B. physalus) and killer whales (Fig. 3A). There was a significant difference in mean prevalence among species ([[chi square].sub.30]=50.6, P<0.01) and Mysticetes had a higher mean prevalence of the barnacle than Odontocetes (5.1% vs. 0.8%). Standard error was greatest for blue (13.8) and fin whales (16.5); all other species had a standard error less than 1.5. Blue, fin, and killer whales also had the highest prevalence per sighting, and 38% of killer whale sightings had barnacles (Fig. 3B). Prevalence per sighting was similar for Mysticetes and Odontocetes (12.7% vs. 14.0%)--a nonsignificant difference (P=0.19). Of the three species most often infested, killer whales represented the majority of individuals used in the analysis (14%), whereas blue whales (1%) and fin whales (0.2%) were rarely encountered. The number of barnacles was, therefore, independent of number of individuals observed ([R.sup.2]=0.00, F=0.10, P=0.08).
Xenobalanus was found in coastal as well as offshore waters of the ETP (Fig. 1). All 22 species were represented in offshore sightings and 28% of individuals encountered were seen in waters greater than 600 km from land, and at a maximum distance of 4287 km from land. Of these offshore occurrences, 39 Xenobalanus were observed on 18 individuals comprising seven species. Xenobalanus was primarily observed in three areas: 1) waters around the Baja California peninsula, 2) the Costa Rica Dome and waters extending west along the 10[degrees]N Thermocline Ridge, and 3) waters off Peru and the Galapagos Archipelago. All three areas are known as areas of increased primary productivity within the ETP (Fig. 1, Fiedler et al., 1991; Pennington et al., 2006).
For killer whales, which were examined in more detail, of the 68 whales infested with 130 barnacles, the mean intensity of infestation was 1.9 barnacles per whale. The greatest numbers of killer whales were photographed in 1998-2003, and these whales also had the greatest intensity of barnacles. This observed increase in intensity was most likely the result of improved photographic techniques. The observed numbers of killer whales with 0, 1, 2, 3, and >3 barnacles were 286, 38, 15, 7, and 8, respectively. This is significantly different from the expected 245, 90, 17, 2, and 0 infested whales, respectively, as predicted by a Poisson distribution with mean 130/354 = 0.367 ([[chi square].sub.5]>300, P<0.00001). The variance (0.941) was much larger than the mean (0.367).
A chart of the worldwide distribution of Xenobalanus was generated from a review of the literature documenting regional occurrences of this genus (Fig. 2). Except for the ETP, Xenobalanus has been reported only within approximately 600 km from land, including the Faroe Islands and the Azores (sites 4 and 8). Figure 2 also demonstrates that Xenobalanus is highly cosmopolitan and has been reported in all oceans, namely in tropical, temperate, and polar waters.
The literature review updates a previous review conducted by Rajaguru and Shantha (1992). Eighteen peer-reviewed accounts have been published since that review, including that of the present study (Table 3). Additionally, ten records of Xenobalanus had not been included in Rajaguru and Shantha's (1992) review. An additional 14 cetacean species are now included: minke whale (Balaenoptera acutorostrata), Bryde's whale, long-beaked common dolphin, Pacific white-sided dolphin, dusky dolphin (Lagenorhynchus obscurus), right whale dolphin (Lissodelphis borealis), humpback whale, vaquita (Phocoena sinus), Burmeister's porpoise (Phocoena spinipinnis), franciscana (Pontoporia blainvillei), clymene dolphin (Stenella clymene), spinner dolphin, rough-toothed dolphin, and Indo-Pacific bottlenose dolphin (Tursiops aduncus).
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Prevalence and intensity of the barnacle
We describe four new host species for the cetacean-specific phoretic barnacle Xenobalanus and document that the barnacle is present on cetaceans far offshore as well as in coastal areas. The fact that Xenobalanus has now been reported on 34 species of cetaceans in both coastal and offshore waters, from the Arctic to Antarctic, either 1) indicates that the barnacle is extremely cosmopolitan (Newman and Ross, 1976; Spivey, 1981), or 2) may suggest that more than one species of the genus Xenobalanus is involved.
Mean prevalence results from this study were lower than those from previous published accounts: 0.2% vs. 4-19% for short-beaked common dolphins (Delphinus delphis) (Pilleri, 1970; Dailey and Walker, 1978), 0.2% vs. 43-56% for bottlenose dolphins (Tursiops truncatus) (Di Beneditto and Ramos, 2004; Toth-Brown and Hohn, 2007), and 0.7% vs. 33-43% for striped dolphins (Stenella coeruleoalba) (Pilleri, 1970; Aznar et al., 2005). Two striped dolphins have been reported with an intensity of more than 100 Xenobalanus (Aznar et al., 2005), but the greatest intensity observed in our study was seven, on killer whales.
Although some differences in prevalence are due to previous reports of maximum, rather than mean, rates, the prevalence of Xenobalanus infestation reported in this study is underestimated because not all barnacles present on the animals were visible in our photographs. Only one side of the animal was photographed, and often part of the body was in the water. On the other hand, prevalence reported in many previous studies may have been overestimated when rates were based on mortality events and strandings. Because stranded animals are not usually healthy, the reported rates could represent an abnormal presence of the barnacle, as was observed in Aznar et al. (2005). Differences may also be related to habitat. Moreover, previous reports have primarily been composed of data from coastal areas, whereas our study was focused on pelagic waters.
Factors affecting the presence of Xenobalanus
Other behavioral and environmental factors may also affect barnacle presence on cetaceans within the ETP. Swimming speed of the host has been shown to correlate negatively with intensity of the whale lice Isocyamus delphini (Balbuena and Raga, 1989) and has been hypothesized as an inversely proportional factor in Xenobalanus settlement (Orams and Schuetze, 1998; Aznar et al., 2005). In our study, blue whales had the greatest mean intensity of Xenobalanus and have been shown to sustain cruising speeds up to 33 km/hr (Yochem and Leatherwood, 1985), indicating that swimming speed may not be a primary factor in host species selection for Xenobalanus. Abrasive breaching and slapping behavior of the host may scour barnacles and inhibit settlement; however, some barnacles appear resistant (Felix et al., 2006; Sakai et al., 2006). In the ETP, deep-diving sperm whales (Physeter macrocephalus) and beaked whales (Mesoplodon spp.) were not hosts, indicating that dive depth of the host may limit the settlement of the barnacle on these species. Orams and Schuetze (1998) and Toth-Brown and Hohn (2007) have suggested an environmental correlation in the distribution of Xenobalanus that is similar to that observed between primary production and barnacle presence in the ETP. Plankton abundance in oligotrophic areas of the ETP may be below a critical threshold for the filter-feeding barnacles and may thus indirectly limit the presence of Xenobalanus.
The intensity of barnacles on killer whales in the ETP was not randomly distributed. There were more whales with no barnacles and with three or more barnacles than would be expected if barnacles settled randomly on killer whales, indicating that if Xenobalanus larvae settle, it is most often in groups of three or more. This aggregated or contagious distribution could occur as a result of: 1) a chemical cue emitted from the host that induces settlement (Nogata and Matsumura, 2005), 2) a chemical cue emitted from conspecifics that induces settlement (Knight-Jones, 1953), which was suggested for Xenobalanus by Aznar et al. (2005), 3) patchily distributed barnacle larvae, or 4) an inability of the host to slough newly settled larvae (Ridgway et al., 1997). The low variance in prevalence and the nonuniform distribution of Xenobalanus sightings within the ETP indicate that most species are equally selected and that barnacle recruitment may be the result of patchily distributed larvae.
Xenobalanus has been reported on a wide variety of cetacean hosts, and this apparent lack of specialization could provide insight into evolutionary age of Xenobalanus. Various species of cyamid whale lice are highly specialized for a particular species of right whale (Eubalaena spp., Kaliszewska et al., 2005). Xenobalanus is more of a generalist than whale lice, given its apparent ability to settle on various cetacean hosts, which may indicate that its evolution and relationship with cetaceans may be more recent than that of other cetacean commensals, and that its specialization to host species has not yet occurred. Coronulid whale barnacles did not appear in the fossil record until approximately 23 million years ago (Newman and Ross, 1976; Seilacher, 2005), after the appearance of Mysticetes and Odontocetes in the fossil record approximately 35 million years ago. However, it is unknown at what point the genus Xenobalanus arose, and presently no data exist on the evolutionary age of cyamids for comparison. In the ETP, Xenobalanus, appearing on almost every cetacean species encountered, did not exhibit the degree of host specialization observed in whale lice. With a lack of data on evolutionary age, these findings support only the hypothesis that Xenobalanus is a generalist cetacean barnacle.
The relationship between commensals and their hosts, which can indicate host movement and host distributional patterns, is often used to make inferences into the biology and ecology of the host. Comparison of internal parasite fauna has helped distinguish stocks, determine stock associations, track large-scale movements, and identify new recruits to populations in many species of fish, elasmobranchs, invertebrates, and marine mammals (Williams et al., 1992). Among marine mammals, intestinal parasites, whale lice, and barnacles have proven useful for tracking migrations of gray whales (Eschrichtius robustus; Killingley, 1980) and identifying stocks and the social structure of pilot whales (Globicephala melas; Balbuena and Raga, 1993), and have been useful for tracking general movement patterns of wide ranging, elusive cetacean populations without the use of expensive tagging equipment.
Our results indicate that Xenobalanus, however, would not be useful as a biological tag. Within the ETP, Xenobalanus is widely distributed and a single, definitive source or home range was not determined for this species. However, this is the first study where distribution of Xenobalanus has been systematically examined on a large scale and it is possible that the few offshore observations within the ETP are not representative of global distribution. Although Xenobalanus could not be used as a biological tag to track the movements of cetaceans within the ETP in this study, the potential use of Xenobalanus as a biological tag should not be abandoned completely. Increased knowledge of the biology of the barnacle, such as host-selection criteria, environmental tolerance limits, and early life history strategies could provide a finer resolution of the phoretic relationship with cetacean species that would enable the use of Xenobalanus as a biological tag in future studies. This and other research on Xenobalanus will form a useful part of the study of cetacean biology and ecology.
Funding for travel and living expenses for E. A. Kane was provided by the Evan Frankel Foundation. We thank J. Barlow, M. Kretzmann, and W. Perrin for reviewing the manuscript before submission, as well as D. Fertl and two anonymous reviewers for their helpful comments. We also thank N. Black and the many scientists and researchers who donated photographs, references, and information for the project.
Manuscript submitted 28 January 2008. Manuscript accepted 17 June 2008.
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Emily A. Kane (contact author) (1, 2)
Paula A. Olson (2)
Tim Gerrodette (2)
Paul C. Fiedler (2)
Email address for E. A. Kane: email@example.com
(1) Southampton College 239 Montauk Highway Southampton, New York 11968
(2) National Marine Fisheries Service, NOAA Southwest Fisheries Science Center 8604 La Jolla Shores Dr. La Jolla, California 92037
Present address for contact author (E. A. Kane): Texas A&M University at Galveston 5007 Avenue U Galveston, Texas 77551
Table 1 Summary of photographic data collected for cetaceans in the eastern tropical Pacific Ocean from 1977 through 2003, including the number of usable photographs ("photographs"), number of sightings ("sightings"), number of identifiable individual cetaceans ("individuals"), and number of identifiable individuals infested with Xenobalanus ("infested individuals"). * Denotes newly reported hosts of Xenobalanus that were determined from this study. Species Common name Years Balaenoptera edeni * Bryde's whale 2003 Balaenoptera musculus blue whale 2003 Balaenoptera physalus fin whale 2003 Delphinus capensis * long-beaked common 2003 dolphin Delphinus delphis short-beaked common 2003 dolphin Feresa attenuata pygmy killer whale 2003 Globicephala macrorhynchus short-finned pilot 2003 whale Grampus griseus Risso's dolphin 2003 Lagenodelphis hosei Fraser's dolphin 2003 Lagenorhynchus obliquidens Pacific white-sided 2003 dolphin Lagenorhynchus obscurus dusky dolphin 2003 Megaptera nouaeangliae * humpback whale 2003 Mesoplodon spp. unidentified 2003 Mesoplodon Orcinus orca killer whale 1977-2003 Peponocephala electra melon-headed whale 2003 Physeter macrocephalus sperm whale 2003 Pseudorca crassidens false killer whale 2003 Stenella attenuata pantropical spotted 2003 dolphin Stenella coeruleoalba striped dolphin 2003 Stenella longirostris * spinner dolphin 2003 Steno bredanensis rough-toothed 2003 dolphin Tursiops truncatus bottlenose dolphin 2003 Total Species Photographs Sightings Balaenoptera edeni * 415 30 Balaenoptera musculus 513 17 Balaenoptera physalus 92 4 Delphinus capensis * 228 13 Delphinus delphis 1146 48 Feresa attenuata 25 1 Globicephala macrorhynchus 1551 34 Grampus griseus 155 12 Lagenodelphis hosei 34 1 Lagenorhynchus obliquidens 5 1 Lagenorhynchus obscurus 245 11 Megaptera nouaeangliae * 504 12 Mesoplodon spp. 40 2 Orcinus orca 1160 49 Peponocephala electra 17 1 Physeter macrocephalus 215 9 Pseudorca crassidens 49 2 Stenella attenuata 1281 76 Stenella coeruleoalba 845 51 Stenella longirostris * 770 39 Steno bredanensis 118 12 Tursiops truncatus 600 61 Total 10,008 486 Infested Species Individuals individuals Balaenoptera edeni * 43 3 Balaenoptera musculus 24 9 Balaenoptera physalus 6 1 Delphinus capensis * 69 2 Delphinus delphis 287 3 Feresa attenuata 11 0 Globicephala macrorhynchus 297 9 Grampus griseus 58 1 Lagenodelphis hosei 6 0 Lagenorhynchus obliquidens 2 0 Lagenorhynchus obscurus 68 4 Megaptera nouaeangliae * 34 1 Mesoplodon spp. 3 69 Orcinus orca 354 0 Peponocephala electra 9 0 Physeter macrocephalus 19 0 Pseudorca crassidens 11 0 Stenella attenuata 326 4 Stenella coeruleoalba 319 18 Stenella longirostris * 271 3 Steno bredanensis 41 0 Tursiops truncatus 252 5 Total 2510 132 Table 2 Dates and geographic locations (latitude and longitude) for sightings of newly documented cetacean hosts of Xenobalanus in the eastern tropical Pacific Ocean in 2003. Data are the following: total number of individuals of the species photographed ("individuals"), total number of these individuals observed with barnacles ("infested individuals"), and barnacle intensity and anatomical location on the host ("intensity and location on the host"). Intensity Infested and location Host Individuals individuals on the host Balaenoptera edeni 64 3 4 on dorsal Bryde's whale fin Delphinus capensis 69 1 1 on right long-beaked pectoral common dolphin flipper Megaptera novaeangliae 34 1 1 on dorsal humpback whale fin Stenella longirostris 99 1 1 on left orientalis pectoral eastern spinner dolphin flipper Stenella longirostris hybrid 91 1 1 on dorsal whitebelly spinner fin dolphin Stenella longirostris 32 1 2 or more on southwestern right southwestern flipper spinner dolphin pectoral Geographic Host Date location Balaenoptera edeni 03 November 2003 09.012[degrees]S Bryde's whale 079.302[degrees]W Delphinus capensis 12 August 2003 25.620[degrees]N long-beaked 109.456[degrees]W common dolphin Megaptera novaeangliae 05 November 2003 06.414[degrees]S humpback whale 081.176[degrees]W Stenella longirostris 15 August 2003 21.448[degrees]N orientalis 108.084[degrees]W eastern spinner dolphin Stenella longirostris hybrid 20 August 2003 08.857[degrees]N whitebelly spinner 145.098[degrees]W dolphin Stenella longirostris 14 October 2003 05.084[degrees]S southwestern 097.974[degrees]W southwestern spinner dolphin Table 3 Geographic regions and corresponding citations for each region where Xenobalanus has been documented on cetaceans worldwide. "Circle" refers to the regions encircled in Figure 2. References cited in Rajaguru and Shantha (1992) have been omitted individually, but are included under the citation for Rajaguru and Shantha (1992). Additional data about new hosts determined in the present study are available in Table 2. Circle Geographic region Citation 1 Pacific Northwest United Rajaguru and Shantha (1992) States and Canada 2 Greenland Rajaguru and Shantha (1992) 3 Northern Scandanavian Rajaguru and Shantha (1992) peninsula 4 Fertie Islands Rajaguru and Shantha (1992) 5 Scotland and Shetland Islands Rajaguru and Shantha (1992) 6 Belgium Rajaguru and Shantha (1992) 7 Western Mediterranean and Raga and Carbonell (1985), Iberian Peninsula Rajaguru and Shantha (1992), Aguilar and Raga (1993), Resendes et al. (2002), Aznar et al. (2005) 8 Azores Rajaguru and Shantha (1992) 9 East coast United States and Rajaguru and Shantha (1992), the Bahamas Toth-Brown and Hohn (2007) 10 Gulf of Mexico Spivey (1981), Jefferson et al. (1995) 11 Southern California and Baja Dailey and Walker (1978), Brownell et al. (1987), Peninsula Samaras (1989), This study 12 Pelagic ETP This study 13 Costa Rica Dome, Galapagos, Van Waerebeek et al. (1990, and Peru 1993), Reyes and Van Waerebeek (1995), Palacios et al. (2004), This study 14 Southeast coast of Brazil Brownell (1975), Young and Uruguay (1991), Rajaguru and Shantha (1992), Di Beneditto and Ramos (2000, 2001, 2004) 15 Northwestern coast of Africa Van Bree (1971), Rajaguru and Shantha (1992), Addink and Smeenk (2001) 16 South Africa and Namibia Rajaguru and Shantha (1992) 17 Southern India Rajaguru and Shantha (1992), Karuppiah et al. (2004) 18 Philippines, South China Sea, Parsons et al. (2001) Hong Kong 19 Japan Uchida and Jun (2000), Sakai et al. (2006) 20 East coast of Australia Rajaguru and Shantha (1992), Orams and Schuetze (1998) 21 Mawson and Davis seas, Bushev (1990) Antarctica 22 Riiser-Larsen and Lazarev Bushev (1990) Seas, Antarctica 23 Shetland Islands, northwest Bushev (1990) Weddell Sea, Antarctica 24 Bellinghausen Sea, Antarctica Bushev (1990)
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|Author:||Kane, Emily A.; Olson, Paula A.; Gerrodette, Tim; Fiedler, Paul C.|
|Date:||Oct 1, 2008|
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